Hydraulic torque wrenches are precision tools which are used to torque and untorque assemblies to a high degree of accuracy. This can be extremely important in applications such as a gas turbine engine and an aircraft frame. These applications require central balanced torque, to eliminate friction and side loading effects as are found in some hydraulic and/or mechanical type wrenches using an offset, inaccurate torquing method. It is critical when assembling such devices that a highly accurate amount of torque is applied to bolts and other types of threaded connectors to ensure the structural security of the connection made. However, since standard torque wrenches are not sufficient for applying the required amount of torque, hydraulic torque wrenches were developed. Other applications in which hydraulic torque wrenches are commonly employed are in driving winches, spring winding apparatus, pipe die threading, and the fastening of various devices such as nuts and bolts.
Commonly, hydraulically actuated torque wrenches comprise a cylindrical member having an opening sized and shaped to engage a workpiece, such as a socket or the head of a bolt or other threaded connector, and apply torque (i.e., rotational force) thereto. Most often, the opening is splined to facilitate engagement of the workpiece. The cylindrical member is fitted with at least one and most commonly a plurality of studs which extend therefrom. These studs are equidistant from the actuator center line, and are acted upon by the action of a hydraulically driven piston and cylinder arrangement to controllably rotate the cylindrical member, which thereby applies accurate output torque to a workpiece engaged by the opening.
Most commonly, the cylindrical member having the opening which accommodates the workpiece is disposed within a second, larger cylindrical member from which depend the stud or studs. In this way, a ratcheting relationship between the inner cylindrical member and the outer cylindrical member can be provided. In so doing, it would not be necessary to disengage the hydraulic cylinders from the outer cylindrical member studs to continue rotation of the inner cylindrical member in a first direction. Rather, the push-pull hydraulic cylinders can reverse direction and return to their starting point without applying torque or untorque forces to the workpiece, because the ratcheting relationship between the inner cylindrical member and the outer cylindrical member keeps the inner cylindrical member stationary while the outer cylindrical member is rotated back to its initial position. Because of this ratcheting action, however, torque applied to a workpiece is applied in an intermittent fashion, because there is no torque being applied as the hydraulic pistons (and thereby the outer cylindrical member) are returning to their original position.
It would be desirable to provide an apparatus and method capable of efficiently providing substantially continuous torque to a workpiece in a first mode and applying intermittent yet increased power torque to the workpiece in a second mode.